WRONG BILLING: MISINFORMATION

MTN has really done me in! I upgraded my mtn account in March and recieved my new steppa tabket and prorata data on first april. I upgraded my contact in March after having been told by the MTN call center folks that the contract that was running at the time was due to expire end of March. At the time of doing the upgrade I was told that at the end of may I would pay the upgrade fee of about one hundred and something rands, and I would only start paying for the upgraded contact amount end of may as end of April would pay for the invoice of March. However, I have gotten the shock of my life after having being told that my upgrade fee / claw back fee is 600 and something rands and not the 100 I was told about. I'm being told that this is because I upgraded before it was time to upgrade! This is all brand new information to me! As I was told by MTN call agents themselves that march wad a good time to upgrade and they didn't tell me about any claw back fee that would be 600: and something! My total invoice according to MTN is 1600 I do not accept this account and I want this error cleared ASAP!